Free-radical generating aromatic diols, polycarbonates containing thermal labile groups and their conversion to polycarbonate block copolymers

ABSTRACT

Bisphenols containing free-radical generating groups, such as bissilylpinacolate groups, are provided. These bisphenols can be used to make free-radical generating polycarbonate macroinitiators having thermally labile groups which can be heated with vinyl monomers, such as styrene to make polycarbonate block copolymers.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to copending application Ser. No. 07/404,287, filed9/7/89 for Peroxide Terminated Polycarbonates, Preparation Thereof andConversion to Copolymers, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to the use of free-radical generatingaromatic diols for preparing polycarbonates having thermal labilefree-radical generating groups in the backbone. More particularly, thepresent invention relates to the employment of free-radicalpolymerizable organic monomers, such as styrene in combination withpolycarbonates having thermally labile free-radical generating groups toproduce polycarbonate block copolymers upon thermolysis.

Prior to the present invention, as shown by Crivello, U.S. Pat. Nos.4,584,356 and 4,677,169, silicone-organic block copolymers were providedby heating a mixture of a silicone prepolymer having chemically combinedpinacolate groups and a free-radical polymerizable organic monomer, suchas styrene, to produce silicone-organic block copolymers.

As discussed in copending application Ser. No. 07/404,287, polycarbonateblock copolymers can be made by the reaction of a peroxide terminatedpolycarbonate with an ethylenically unsaturated compound, such asstyrene, to produce the corresponding polycarbonate-polystyrene blockcopolymer. The resulting copolymers have been found capable ofcompatabilizing blends of a polycarbonate with another organic polymer.

SUMMARY OF THE INVENTION

The present invention is based on the discovery that a free-radicalgenerating aromatic diol having the formula,

    HO--R--Q--R--OH,                                           (1)

where R is a divalent C.sub.(6-13) aromatic organic radical, and Q is adivalent thermally labile free-radical generating group as definedbelow, can be phosgenated together with bisphenols, such as bisphenol-A,to provide polycarbonates having free-radical generating capability uponthermolysis. As a result, polycarbonate block copolymers can bespontaneously formed by the chain growth at both ends of themacrodiradicals which are produced by the thermal decomposition of thethermally labile residues of the polycarbonate. A variety ofpolycarbonate block copolymers can be prepared utilizing this method ofsynthesis in view of the wide variety of vinyl monomers which can beused.

STATEMENT OF THE INVENTION

There is provided by the present invention polycarbonate blockcopolymers comprising polycarbonate blocks and organic polymeric blockssubstantially free of chemically combined carbonate units, whichpolycarbonate block copolymers comprise the reaction product offree-radical polymerizable organic monomer and a polycarbonatemacroinitiator having in its backbone, or in its terminal position, atleast one chemically combined thermally labile group capable of formingfree-radicals upon thermolysis.

Aromatic organic radicals included by R of Formula 1 are C.sub.(6-13)divalent aromatic organic radicals, such as phenylene, tolylene, xylene,and naphthalene; divalent groups included within Q of Formula 1 are, forexample, ##STR1## where X is a member selected from N═N and --O--O--, R¹is the same or different C.sub.(1-13) monovalent organic radical, suchas methyl or phenyl, and n is 0 or 1.

Some of the aromatic diols included within Formula 1 are, for example,##STR2##

Polycarbonates having thermally labile groups in their backbone, can bemade by phosgenating a mixture of a free-radical generating aromaticdiol included within Formula 1, and a dihydric phenol included withinthe formula

    HOR.sup.2 OH                                               (2)

where R² is a C.sub.(6-13) divalent aromatic hydrocarbon radical.Dihydric phenols included within formula (2) are, for example,2,2-bis-(2-hydroxyphenyl)propane, 2,4'-dihydroxybiphenylmethane,bis-2(2-hydroxyphenyl)methane, 2,2-bis-(4-hydroxyphenyl)propane,referred to hereinafter as "bisphenol A" or "BPA",1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)propane,4,4'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl,2,4-dihydroxybenzophenone, 4,4'-dihydroxydiphenylsulfone,2,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfoxide,4,4'-dihydroxydiphenylsulfide, tetramethyl bisphenol,1, 1,1-dichloro-2,2-bis(4-hydroxyphenyl) ethylene, 6,6'-dihydroxy-3,3,3',3'-tetramethyl-bis-,1,1'spiroindane, oxydiphenol,4,4'-[1,4-phenylenebisoxy]bisphenol, ##STR3##

The polycarbonates having free radical generating Q groups of formula 1,in the backbone referred to hereinafter the "polycarbonatemacroinitiator" or "macroinitiator" can have a M_(n) of 1000 to1,000,000 and an M_(w) of 2,000 to 1,000,000 grams/mols along with adispersity of a 1.5 to 10 as determined using polystyrene standards. ¹HNMR spectroscopy shows that there can be from 0.5 to 20 mol % of Qgroups in the polycarbonate backbone.

Suitable free-radical polymerizable monomers or mixtures thereof, whichcan be coreacted with the macroinitiator are, for example, styrene,4-methylstyrene, 4-1-butylstyrene, 2-chlorostyrene, 4-bromostyrene,4-chloromethylstyrene, vinyl napthalene, n-vinylcarbazole, vinylacetate, vinyl anthracene, acrylonitrile, methacrylonitrile, maleicanhydride, ethyl vinyl ether, methyl methacrylate, vinyl pyridine, butylacrylate, butadiene, isoprene, lauryl acrylate, vinyl carbonate, diethylmaleate, methyl α-cyanoacrylate.

In the practice of the present invention, a macroinitiator can be usedto carry out block polymerizations simply by dissolving it into afree-radically polymerizable organic monomer which hereinafter means oneor a mixture of several organic monomers as previously defined, ininstances where such dissolution can be achieved. Depending upon the mol% of the thermally labile Q groups in the polycarbonate macroinitiatorand the weight proportion of the polycarbonate macroinitiator which isused in combination with the free-radical polymeriable organic monomer,the nature of the resulting polycarbonate block copolymer can varyconsiderably. It is preferred, for example, to utilize polycarbonatemacroinitiator having from about 0.5 mol % to 20 mol %, and preferrably1 mol % to 10 mol % of thermally labile Q groups to providepolycarbonate block copolymers upon thermolysis with the free-radicalpolymerizable organic monomer. On the other hand, depending upon thenature of the polycarbonate block copolymer desired, there can be usedfrom 10 parts to 100 parts by weight of polycarbonate macroinitiator,per 100 parts by weight of the free-radical polymerizable organicmonomer.

In particular instances, it has been found advantageous to employ aninert organic solvent in combination with the free-radical polymerizableorganic monomer to facilitate the dissolution of the polycarbonatemacroinitiator and its coreaction with the free-radical polymerizableorganic monomer. Examples of such solvents are, toluene, chlorobenzene,and cyclohexanone.

Temperatures in the range of from 40° C. to 180° C. can be used toeffect the thermolysis of the polycarbonate macroinitiator to achievefree-radical polymerization and formation of the polycarbonate blockcopolymer and preferably temperatures in the range of from 60° C. to140° C.

The polycarbonate block copolymers of the present invention can be usedas compatibilizers for polycarbonate blends with vinyl homopolymers,such as polystyrene, polymethylmethacrylate, polyvinyl chloride,polybutadiene, and the like. They can also compatabilize vinylcopolymers such as styrene-co-butadiene and styrene-acrylonitrile.

In order that those skilled in the art will be better able to practicethe present invention the following examples are given by way ofillustration and not by way of limitation. All parts are by weightunless otherwise indicated.

EXAMPLE 1

4,4'-dihydroxy-O,O-bis(trimethylsilyl)benzopinacol having the formula,##STR4## where Ph is phenyl, was prepared as follows:

There was added 105.78 grams(0.50 mol) of N,O-bis(trimethylsilyl)acetamide over a period of 25 minutes to a stirred solution of 99.1grams(0.50 mol) of 4-hydroxybenzophenone and 1 liter of tetrahydrofuran.The solution was allowed to stir for one hour under ambient conditions.The solvent was then removed and the resulting oil distilled in vacuo(boiling point 154°-156° C.) to yield 123.01 grams(0.45 mol 90%) of thedesired product. Based on the method of preparation and the ¹ H--NMRspectra, the product was 4-(trimethylsilyloxy)benzophenone.

There was added 1.27 grams (0.05 mol) of magnesium metal (30 mesh) and 5mL of N,N,N',N'-tetramethylurea to a stirred solution under ambientconditions containing 27.0 grams of the above4-(trimethylsilyloxy)benzophenone, 10.86 grams(0.1 mol) oftrimethylchlorosilane and 50 mL of tetrahydrofuran. The reaction mixturewas heated at reflux for one hour and allowed to stir for an additional12 hours. The solvent was then removed in vacuo, leaving an oil whichwas slurried with 200 mL of diethyl ether and filtered. The filtrate wascollected and the ether removed in vacuo. The resulting oil was purifiedby flash chromatography to yield 48.40 grams(84%) of the product. Basedon method of preparation and ¹ H--NMR spectrum, the product was amixture of corresponding d,l and meso stereoisomers of4,4'-bis(dimethylsilylloxy)--O,O--bis(trimethylsilyl)benzopinacol.

There was added 50 mL of a 5% aqueous potassium carbonate solution to astirred solution under ambient conditions containing 46 grams(0.08 mol)of the above benzopinacol and 150 mL of methanol. After 1 hour, a solidprecipitated from a reaction mixture and an additional 100 mL of waterwas slowly added. The reaction was stirred for an additional 3 hours.The product was isolated from solution by filtration and dried in vacuoat room temperature to yield 26.60 grams (69% of product). Based onmethod of preparation, and ¹ H--NMR spectrum, the product was4,4'-dihydroxy--O,O--bis(trimethylsilyl)benzopinacol.

EXAMPLE 2

There was added 5.0 mL of a 0.10M methylene chloride solution oftriethylamine to a solution of 11.41 grams(0.05 mol) of bisphenol A and1.36 grams(0.0025 mol) of the above dihydroxy benzopinacol. The pH ofthe reaction mixture was increased to 10 by an addition of a few dropsof a 50% by weight aqueous sodium hydroxide solution Phosgene was thenpassed into the reaction mixture while it was vigorously stirred for 40minutes at a flow rate of 0.35 grams/minute while the pH was maintainedbetween 9-11 by continuous addition of the sodium hydroxide solution.The reaction mixture was purged with nitrogen and then washed once with500 mL of a 5% acetic acid solution, and three times with one liter ofwater. The methylene chloride layer was collected and a productprecipitated from the solution by addition to methanol. The precipitatedproduct was filtered and dried overnight in vacuo. Based on the methodof preparation and the GPC analysis, there was obtained a polycarbonatehaving an M_(n) equal to 34,000, M_(w) equal to 67,000, and M_(w) /M_(n)equal to 1.95. The identity of the product was further confirmed by ¹H--NMR analysis. The number of benzopinacol repeat groups in thepolycarbonate chain was determined to be 4.38, based on GPC analysis.

EXAMPLE 3

A continuous stream of argon was passed into a mechanically stirredsolution of 100 mL of styrene and 5 grams of the polycarbonatemacroinitiator of Example 3. After a period of 15 minutes, the reactionmixture was heated to 100° C. for a period of 90 minutes in a constanttemperature bath. After such time, the solution was removed from thebath, allowed to cool and poured into methanol precipitate product. Theproduct was isolated from solution by filtration, dried overnight at 60°C. in vacuo. The product was then redissolved in chloroform andreprecipitated by addition of methanol. There is obtained 13.5 grams ofpolymeric product. Based on method of preparation and GPC analysis, theproduct was a polycarbonate-polystyrene block copolymer having an M_(n)of 60,515, M_(w) of 239,298, and M_(w) /M_(n) of 3.94.

A three component compatibilized blend is prepared by melt mixing in anextruder at 230° C.-250° C., 20 parts of the abovepolycarbonate-polystyrene block copolymer, 50 parts of a polycarbonateresin having an M_(n) of about 15,000 and an M_(w) of about 40,000 and50 parts of a polystyrene resin having an M_(n) of about 80,000 and anM_(w) of about 190,000. The melt is allowed to cool and then molded 240°C.-260° C. at 1500 psi.

The molded compatabilized blend is found to have improved interfacialdispersion and impact properties as compared to a molded blend of thesame component free of the polycarbonate-polystyrene compatabilizer.

Example 4

A continuous stream of argon was passed into a mechanically stirredsolution containing 60 ml of chlorobenzene, 3 grams of the polycarbonatemacroinitiator of Example 2, and 15.6 grams of styrene. After a periodof 15 minutes, the reaction mixture was heated to 100° C. for a periodof 8 hours in a constant temperature bath. After such time, the solutionwas removed from the bath, allowed to cool and poured into methanol toeffect the precipitation of the product. The product was isolated fromsolution by filtration, dried for 48 hours at 80° C. in vacuo. There wasobtained 6.02 grams of product. Based on the method of preparation andGPC analysis, the product was a polycarbonate-polystyrene copolymerhaving an M_(n) of 21,800, M_(w) of 76,825, and M_(w) /M_(n) of 3.523.

Although the above examples are directed to only a few of the very manyvariables which can be employed in the practice of the presentinvention, it should be understood that the present invention isdirected to the use of a much broader variety of free-radical generatingaromatic diols, dihydric phenols which can be used in combination withsuch thermally labile group containing aromatic diols, to producefree-radical macropolycarbonate initiators and free-radicalpolymerizable organic monomers which can be used to product a widevariety of polycarbonate block copolymers.

What is claimed is:
 1. Polycarbonate block copolymers comprising organicpolymeric blocks joined to polycarbonate blocks by an[oxyphenylene-(trimethylsiloxy)phenyl]methyl linkage of the formula,##STR5## resulting from the thermolysis of a mixture of a free radicalpolymerizable organic monomer and a polycarbonate macroinitiator havingin its backbone at least one chemically combined thermally labile groupresulting from the phosgenation of a mixture of a dihydroxy-O, O-bissubstituted benzopinacol and a dihydric phenol.
 2. A block copolymer inaccordance with claim 1, where the free-radical polymerizable organicmonomer is styrene.
 3. A polycarbonate block copolymer in accordancewith claim 1, where the dihydric phenol is bisphenol A.
 4. A blockcopolymer in accordance with claim 1, where the free-radicalpolymerizable organic monomer is methyl methacrylate.
 5. A blockcopolymer in accordance with claim 1, where the free-radicalpolymerizable organic monomer is acrylonitrile.
 6. A block copolymer inaccordance with claim 1, where a mixture of free-radical polymerizableorganic monomers is used.
 7. A block copolymer in accordance with claim1, where the free-radical polymerizable organic monomer is vinylchloride.